package com.open.capacity.common.util;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class SnowUtil {


    /**
     * 起始的时间戳
     */
    private long START_STMP = 1480166465631L;

    /**
     * 每一部分占用的位数
     */
    private long SEQUENCE_BIT = 12; //序列号占用的位数
    private long MACHINE_BIT = 5;  //机器标识占用的位数
    private long DATACENTER_BIT = 5;//数据中心占用的位数

    /**
     * 每一部分的最大值
     */
    private long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
    private long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);

    /**
     * 每一部分向左的位移
     */
    private long MACHINE_LEFT = SEQUENCE_BIT;
    private long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
    private long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;
    @Value("${snow.flake.datacenterId:1}")
    private long datacenterId;  //数据中心
    @Value("${snow.flake.machineId:1}")
    private long machineId;    //机器标识
    private long sequence = 0L; //序列号
    private long lastStmp = -1L;//上一次时间戳

    public  SnowUtil() {
        if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
            throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0");
        }
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
        }
        this.datacenterId = datacenterId;
        this.machineId = machineId;
    }

    /**
     * 产生下一个ID
     *
     * @return
     */
    public synchronized long nextId() {
        long currStmp = getNewstmp();
        if (currStmp < lastStmp) {
            throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
        }
        sequence = (sequence + 1) & MAX_SEQUENCE;
//        if (currStmp == lastStmp) {
//            //相同毫秒内，序列号自增
//            sequence = (sequence + 1) & MAX_SEQUENCE;
//            //同一毫秒的序列数已经达到最大
//            if (sequence == 0L) {
//                currStmp = getNextMill();
//            }
//        } else {
//            //不同毫秒内，序列号置为0
//            sequence = 0L;
//        }

        lastStmp = currStmp;

        return (currStmp - START_STMP) << TIMESTMP_LEFT //时间戳部分
                | datacenterId << DATACENTER_LEFT      //数据中心部分
                | machineId << MACHINE_LEFT            //机器标识部分
                | sequence;                            //序列号部分
    }

    private long getNextMill() {
        long mill = getNewstmp();
        while (mill <= lastStmp) {
            mill = getNewstmp();
        }
        return mill;
    }

    private long getNewstmp() {
        return System.currentTimeMillis();
    }
}